Validation of a derived version of the IPF-specific Saint George’s Respiratory Questionnaire

Abstract

Background Health-related quality of life (HRQL) is impaired in patients with idiopathic pulmonary fibrosis (IPF). HRQL is often measured using the St. George’s Respiratory Questionnaire (SGRQ) despite the development of an IPF-specific version (SGRQ-I). Using data from a real-world cohort of patients with IPF, we aimed to transform SGRQ into a derived version of SGRQ-I, SGRQ-Ider, to examine the cross-sectional and longitudinal validity of SGRQ-Ider and to compare SGRQ-Ider to SGRQ-I. Methods Based on results from SGRQ, SGRQ-Ider was derived applying the algorithm used to develop SGRQ-I. Of the 50 items in SGRQ, 34 items were retained in SGRQ-Ider. Response options for seven items were collapsed and minor adjustments were made to the weights of two items after correspondence with the developers of SGRQ-I. Cross-sectional validation, responsiveness and minimal clinically important difference (MCID) were assessed by comparison to other HRQL instruments, pulmonary function tests and 6-min walk test performed at baseline, 6 and 12 months. Furthermore, the association between SGRQ-Ider scores and mortality was examined. Results A total of 150 IPF patients participated and 124 completed follow-up at 12 months. SGRQ-Ider performed comparably to SGRQ-I with a high concurrent validity, good test–retest reliability and high known-groups validity. SGRQ-Ider was responsive to change in HRQL and physiological anchors. MCID of SGRQ-Ider for improvement and deterioration was 3.5 and 5.7, respectively. SGRQ-Ider scores were associated with mortality in both univariate (HR 1.82, 95% CI 1.42–2.34 per 20-point increase) and multivariate analyses (HR 1.57, 95% CI 1.20–2.05 per 20-point increase). Conclusions The SGRQ-Ider is a valid, reliable and responsive HRQL instrument in patients with IPF and has psychometric properties comparable to SGRQ-I. Thus, SGRQ results can reliably be transformed into the SGRQ-Ider. The MCID estimates were calculated for improvement and deterioration separately. Increasing SGRQ-Ider score was associated with increased mortality.

Diagnostic delay in IPF impacts progression-free survival, quality of life and hospitalisation rates

“… 19 27 28 Consequently, we used an IPF-specific version of the SGRQ derived from the original SGRQ, which confirmed the association between a long diagnostic delay and impaired quality of life. 20 Also, the original SGRQ and CAT have both been used in patients with IPF, and have proven to possess validity to differentiate patients who progress over time. 29–31 …”

“…19 27 28 Consequently, we used an IPF-specific version of the SGRQ derived from the original SGRQ, which confirmed the association between a long diagnostic delay and impaired quality of life. 20 Also, the original SGRQ and CAT have both been used in patients with IPF, and have proven to possess validity to differentiate patients who progress over time. [29][30][31] The higher hospitalisation rates in patients with a long diagnostic delay provide an additional and clinically meaningful outcome of increased morbidity in these patients.…”

“…Two quality-of-life questionnaires, the St. George’s Respiratory Questionnaire (SGRQ) and the chronic obstructive pulmonary disease (COPD) assessment test (CAT), were completed at each visit. A validated IPF-specific version of the SGRQ (SGRQ-I der ), analogous to the SGRQ-I was derived from the original SGRQ, as previously described 19 20. In addition, two symptom-specific scores for patient-reported dyspnoea (graded from 0 (when I walk up a hill or one flight of stairs I am not breathless) to 5 (when I walk up a hill or one flight of stairs I am very breathless)) and cough (graded from 0 (I never cough) to 5 (I cough all the time)) were extracted from the CAT questionnaire.…”

Fibroblast activation protein and disease severity, progression, and survival in idiopathic pulmonary fibrosis

“…Patients with IPF were recruited from August 2016 to March 2018 at the three tertiary ILD centers in Denmark (Aarhus, Odense and Copenhagen). In-and exclusion criteria have been reported in studies based on the same cohort on patient related outcome measures and comorbidities in IPF [8][9][10][11][12]. Patients were followed for up to three years.…”

“…Progression after 12 months was observed in 49 patients (33%). The median sFAP in patients with IPF was 49.6 ng/mL (interquartile range (IQR): 43.1-61.6 ng/mL), whereas the median Values are presented as n (%) or mean with standard deviation (SD)[8][9][10][11][12]. FVC: Forced vital capacity; DLCO: Diffusing capacity of the lung for carbon monoxide; 6MWD: 6-minute walk test distance…”